This invention relates to a polycentric hinge for a knee brace or other hinged device, and more particularly to a selectable extension stop for limiting the pivotal movement allowed by the hinge.
When the ligaments surrounding the knee have been traumatized by injury or by surgery, a supporting brace is used which permits controlled pivotal movement of the knee elements to restore their strength and natural range of movement. The brace should protect the knee from lateral and rotational movements and prevent hyperextension of the knee beyond the point of natural articulation. For example, a known knee brace has shin and thigh plates and, extending down both the medial and lateral sides of the leg, a pair of rigid arms which are pivotally connected at the knee by a polycentric hinge. This brace allows the knee to bend but prevents lateral and rotational movements.
Additional knee brace elements have been suggested to prevent the knee from pivoting forwardly beyond a maximum desired articulation, i.e., hyperextending. It has been suggested to provide flexible straps connecting the arms or the shin and thigh plates to prevent a full unbending of the knee. Another brace includes a pair of notches on one of two pivotally connected hinge elements which notches cooperate with a fixed pin and a selectively positionable pin on the other element (U.S. Pat. No. 4,088,130 to Applegate). Another brace provides a fixed stop on a polycentric hinge which engages a pair of shoulders on the ends of two rigid arms having intermeshing gear teeth (U.S. Pat. No. 4,524,764 to Miller et al.). Still another brace provides a pinion stop gear which meshes with and is selectably rotatable about the periphery of each of the hinge gears of a polycentric hinge (U.S. Pat. No. 4,493,316 to Reed et al.). Yet another brace provides a pair of stop pins releasably insertable in the left and right portions of a groove in a bracket disposed adjacent a polycentric hinge (U.S. Pat. No. 4,337,764 to Lerman).
Each of these prior devices suffers from either a lack of adjustability, undue complexity, or a lack of stability. Therefore, it would be desirable to provide a polycentric hinge for a brace having a simple, adjustable and secure means for limiting the pivotal movement of the arms connected by the hinge.